Some companies are obviously great investments -- in hindsight. Sure, we should have bought Starbucks at its IPO and earned amazing returns over the years. Yet for every stock out there screaming "buy me," others simply give us a nudge and a nod. How can we tell tomorrow's obviously great investments from the thousands of pretenders?

The stars' walk of fame
On Motley Fool CAPS, these opportunities can be found among our four-star stocks. In CAPS' proprietary ratings system, they rank higher than most of the other 5,600 companies in the CAPS universe, but they're just shy of superstardom. While all the attention might be focused on their five-star cousins, we can sift through CAPS to find four-star firms approaching greatness. Here's a few to consider this week:

  • Barrick Gold (NYSE: ABX)
  • LDK Solar (NYSE: LDK)
  • Level 3 Communications (Nasdaq: LVLT)
  • On2 Technologies (AMEX: ONT)
  • TASER International (Nasdaq: TASR)

Some of these names might surprise you -- for instance, telecom provider Level 3 Communications. Almost great? It has been delivering online content for years, and while it was a tech darling that crashed at the turn of the millennium, those days are behind it now. Lately, it has been signing deals with the likes of IBM (NYSE: IBM), as well as holding a host of industry-defining patents.

Even familiar names can still offer some of the best opportunities. Perhaps we've just forgotten the potential they still hold. However, the 97,000 investors on CAPS chose these companies as less obvious sources for tomorrow's great buys, so let's see why they might merit your attention.

A stunning achievement
It wasn't that long ago that stun gun maker TASER was subject to questions about its efficacy. Sure, the law-enforcement community loved the virtually immediate compliance it was able to obtain from otherwise unruly or dangerous suspects, but some thought the potential for abuse was too great -- and that the company's ability to follow through wasn't up to the task. New Jersey, for example, is the only state in the nation where it's illegal for police officers to use a TASER, though that's being reconsidered.

The Motley Fool Rule Breakers recommendation is recognized by most as a viable less-than-lethal use of force, and that's led many police departments to put in sizable orders. In its last earnings release, the company reported that several significant orders were placed, while international orders are growing almost exponentially. In fact, one such deal was equivalent to about 4% of total fourth-quarter revenue.

The company is able to put together growing sales and a more palatable use-of-force option, and it has a virtual monopoly on the market -- the only real competition is traditional gun makers like Smith & Wesson (Nasdaq: SWHC). So it's understandable that investors like CAPS player drock743 would not be shocked by stock outperformance:

[TASER] is getting orders in faster then they can process them. The military is using these devices as well as law enforcement agencies worldwide. They truly are an amazing invention that have saved many lives and have saved towns and states millions of dollars in wrongful death lawsuits... These devices give law enforcement an opportunity to temporarily incapacitate a violent subject to take them into custody... This company is currently taking large orders from these agencies, they will get many more as more states approve their use by police... The devices have gotten better ... with some models coming with a built-in video camera which catches the action just prior to the device being deployed to show a judge and jury... They are expensive and they work which spells $$$$ for the investor in the stock.

A great opportunity for you
You've heard directly from CAPS investors on TASER, but do you agree? Is this still investment-grade material? (And what about the other four-star stocks?) On Motley Fool CAPS, you can give your input, which can ultimately influence how they're rated. Outperform or underperform, near-term or well in the future, your opinion counts.

Sign up today for Motley Fool CAPS. It's completely free. Let's us hear what you have to say about the great -- and almost-great -- companies that interest you.

TASER is a Rule Breakers recommendation. See what other shocking stocks are beating the market with a 30-day free trial subscription.

Fool contributor Rich Duprey does not have a financial position in any stocks mentioned in this article. You can see his holdings here. The Motley Fool has a disclosure policy.